336 THE EAR tests, and any granulation tissue should be sent for histological examination. The wound is sutured, and a drain of ribbon gauze is left in the lower end of the incision. Fig. 173. Bone involvement in otitis media. A, Radiograph of right mastoid process showing extensive development of air cells: 1, Zygomatic cells; 2, Condyle of mandible; 3, External acoustic meatus; 4, Cells at tip of process; 5, Marginal cells (the clear area in front of this line indicates the position of the sigmoid sinus); 6, Posterior-superior or petrosal angle cells. B, Cortical mastoidectomy on dry temporal bone: 1, Antrum; 2, Glenpid fossa; 3, External acoustic meatus; 4, Cells at tip of process; 5, Sub- labvrinthme cells; 6, Bulging of sinus plate into operation cavity; 7, Posterior-superior or petrosal angle cells, C, Vertical radiograph of head of patient with acute inflammation of cells at apex of left petrous pyramid: 1, Normal cells of pyramid on right side; 2, Cloudy cells on left side; 3, Anterior arch of atlas; 4, Odontoid process of axis; 5, Mandible. The stitches and the drain are removed under anaesthesia after a week, by which time it is expected that the wound will be healed, apart from the lower end, and the meatus will be dry. Further wound dressings are con- tinued daily until complete union has taken place, and the patient is usually discharged from hospital 2 weeks after operation.